Self-locking fluid operated cylinder

ABSTRACT

A fluid operated cylinder is described having a locking means for holding the piston at one end of the cylinder every other time fluid pressure is applied to the cylinder to drive the piston in one axial direction. A locking means is provided adjacent said one end having a control member that is movable in a limited stroke parallel with and in response to the movement of the piston. The control member is also rotatable. Inclined stepping cam surfaces are provided in the longitudinal path of the control member to step index the control member in one angular direction each time the control member is moved axially. Interlocking elements are provided on the control member and the piston that interlock together when the control member is rotated from a selected angular position and automatically released when the control member is located at the selected angular positions.

mte 1 States Ptnt [1111 ama Slaughter 11 Mar, 26, 11974 1 SELF-LOCKING lFlLlUllD OPEATED CYILENDIER Primary Examiner-Edgar W. Geoghegan Assistant ExaminerAbraham Hershkovitz [76] Inventor: Kemp Slaughter, N. 421

Sycamore st" Spokane, wash Attorney, Agent, or Fzrm-Wells, St. John & Roberts 99202 22 Filed: July 17, 11972 [57] ABSTMW Appl. No.: 272,297

A fluid operated cylinder is described having a locking means for holding the piston at one end of the cylinder every other time fluid pressure is applied to the cylinder to drive the piston in one axial direction. A locking means is provided adjacent said one end having a control member that is movable in a limited stroke parallel with and in response to the movement of the piston. The control member is also rotatable. Inclined stepping cam surfaces are provided in the longitudinal path of the control member to step index the control member in one angular direction each time the control member is moved axially. Interlocking elements are provided on the control member and the piston that interlock together when the control member is rotated from a selected angular position and automatically released when the control member is located at the selected angular positions.

11) Cllaims, 13 Drawing Figures PATENTEU R26 8974 SHEU 1 [1F 3 PEG '1 PAIENTEUmzs um I FIG 11 FIGIQ FIG '10 FIG '13 SELF-LOCKING FlLlUllll) OPERATED CYLINDER BACKGROUND OF THE INVENTION This invention relates to fluid operated cylinders and more particularly to fluid operated cylinders having self-locking features to hold the cylinder rod in one position.

In many applications of fluid operated cylinders, it is desirable to maintain the cylinder in one position to prevent the cylinder from moving to another position to accomplish a particular task. Frequently, the pneumatic or hydraulic fluid system accompanying the cylinder has a fluid blocking system attempting to prevent the movement of fluid should a system failure occur in the control system.

Other means have been developed for locking the piston at a particular position. Many of such devices are classified in the U. S. Patent Office in Class 92 relating to Expandible Chamber Devices under subclass relating to Releasable Stop and Latching Means for Preventing Movement of the Working Member." Illustrative of such devices are those described in U. S. Pat. Nos. 2,012,721; 2,074,772; 2,333,274; 2,394,488; 2,811,951; 2,970,573; 3,010,752; 3,108,319; 3,150,569; 3,173,659; and 3,527,551.

One of the principal objects of this invention is to provide a self-locking fluid operated cylinder having a very simple and efficient means for locking the piston at one end of the cylinder to prevent the piston from moving to the other end of the cylinder should the fluid system fail.

An additional object of this invention is to provide a self-locking fluid operated cylinder having a locking means that is responsive to the movement of the piston for automatically locking the piston at one end of the cylinder. 7

A further object of this invention is to provide a selflocking fluid operated cylinder that automatically locks and unlocks in response to the movement of the piston.

An additional object of this invention is to provide an automatic self-locking cylinder that is fluid operated and which is automatically operated to lock the piston at one end of the cylinder and which may be automatically unlocked by applying fluid pressure on the piston in the same direction.

A further object of this invention is to provide a simple self-locking mechanism that is very reliable yet relatively inexpensive to incorporate in the cylinder.

These and further objects and advantages of this invention will become apparent upon the reading of the following detailed description of a preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of this invention is illustrated in the accompanying drawings, in which:

FIG. 11 shows a front view of a lifting apparatus in which a cylinder incorporating the principal features of the invention is shown lifting a load;

FIG. 2 is a longitudinal cross-sectional view taken along line 2-2 in FIG. 11 illustrating the interior of a cylinder having a locking mechanism for locking the piston at one end of the cylinder in which the locking mechanism includes a control member and a cam indexing mechanism;

FIG. 3 is a cross-sectional view taken along line 33 in FIG. 2;

FIG. 4 is a cross-sectional view taken along line 4-41 in FIG. 2;

FIG. 5 is a cross-sectionalview taken along line 55 in FIG. 2;

FIG. 6 is an isolated perspective view of a portion of the cam indexing mechanism;

FIG. 7 is an isolated perspective view of the control member; and

FIGS. 3-13 inclusive illustrate the operation of the self-locking mechanism in schematic form.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now in detail to the drawings, there is illustrated in FIG. 11 an automatic self-locking cylinder 10 that is fluid operated. The cylinder 10 is mounted on a frame 111. Self-locking cylinder 10 has a rear end 112. that is fixed to an overhead member of the frame by bracket 13. The cylinder 10 has a piston rod 16 extending from a front end 15. The piston rod 16 is connected to a load 17 that is illustrated in the form of a breaker bar. One particular application of the self-locking cylinder is in an aluminum reduction plant in which the cylinder is utilized in a reduction furnace for supporting a breaker bar in an elevated position during the reduction operation and for moving the breaker bar downward to break a formed flux crust at the conclusion of the reduction operation. Fluid lines 20 communicate fluid to and from the cylinder for its operation in the traditional manner.

Specifically, the automatic self-locking cylinder 10 includes a cylinder housing 23 (FIG. 2) with a central cylindrical body 25 and a rear end block 26 and a front end block 27 enclosing the ends of the cylindrical body 25 to form a cylindrical fluid cavity 23 therein having a longitudinal axis.

A piston 30 is movably mounted in the cavity for movement between the end blocks 26 and 27. The piston 30 has piston rings 31 about its circumference to minimize the movement of the fluid past the piston. The piston rod 116 is affixed to the piston 30 and extends through a bore 32 in the end block 27. The other end of the piston rod 116 is connected to a load 17 such as that illustrated in FIG. 1. A bearing 33 is mounted in the end block 27 forming the bore 32. A fluid passageway 35 extends through the end block 205 communicating with the fluid cavity 28 on one side of the piston defining an expandible chamber 37. A fluid passageway 36 extends through the end block 27 communicating with the fluid cavity 23 on the other side of the piston defining an expandible chamber 33. The fluid passageways 35 and 36 communicate with the fluid lines 20. The cylinder 110 may be operated as a single or double-acting cylinder. For the particular application illustrated in FIG. 11, the cylinder is operated as a double-acting cylinder. Fluid pressure is applied through passageway 35 to expand chamber 37 and drive the piston downward to lower the load. The load is raised when fluid pressure is applied to the expandible chamber 33 to drive the piston 30 to end 112. Although shown in a vertical orientation, it should be understood that the locking cylinder may be operated in any orientation including horizontal.

The principal feature of this invention is a locking means 10 that is provided in the expandible chamber 37 for preventing the piston from returning to end every other time the piston moves to end 12 and for automatically releasing the piston every intermediate time the piston is moved to the end 12.

The locking means includes a control member 42 that is axially movable in relation to the housing along the longitudinal axis of the cylinder and is rotatably mounted for rotation about said axis. The locking means 40 further includes a cam means 43 that is positioned in the longitudinal path of the control member for rotating the control member in response to the longitudinal movement of the control member. The locking means 40 further includes an interlocking means 44 that is directly responsive to the rotational movement of the control member 42 for operatively interlocking the piston to the housing adjacent the piston end ll2 when the control member is rotated from one or more preselected angular positions.

The cam means 43 includes two indexing cams 46 and 47 that are axially spaced along the longitudinal axis at end 12 for operatively engaging the control means 42 and incrementally rotating the control member about the longitudinal axis in response to a limited axial movement of the control member 42. The index ing cam 46 is mounted in a bore 50 formed in the end block 26. The indexing cam 46 is locked in the bore 50 by a locking ring 51. A counterbore 53 is formed in the end block 26 concentric with the bore 50 forming a shoulder 54 to receive cam 47. The indexing cam 47 is locked in the counterbore 53 by locking ring 55.

The indexing cam 46 is rather cylindrical in shape having a cam end 58 engaging the base of the bore 54) and a cam end 59 having a plurality (four illustrated) of angularly spaced spirally-inclined cam surfaces 60. Each of the cam surfaces 60 extends an angular distance of approximately 90 between a lobe 6ll and a dwell 62. Each of the cam surfaces 60 is directed from a lobe 61 to a dwell 62 in one rotational direction which is counterclockwise as viewed in FIG. 3. The dwell 62 is terminated by a shoulder 63 forming a pocket 64. As viewed from the side (FIG. 5) the cam surfaces form a somewhat ripsaw tooth configuration as one progresses circumferentially about the cam.

The indexing cam 47 (FIG. 6) includes a cam end 67 engaging the locked ring 55. Indexing cam 47 has a cam end 69 opposing cam end 59. The cam end 69 is substantially a mirror image of the cam end 59 and in cludes equally spaced spirally-inclined cam surfaces 70. Each cam surface 70 extends from a lobe 72 to a dwell 74 terminated by a shoulder 75 to form a pocket 76. The indexing cam 47 is positioned in the counterbore 53 angularly offset with respect to the indexing cam 46 by approximately 45 so that the lobes 611 and 62 and the dwells 62 and 74 are offset approximately 45 to each other, and the surfaces 60 and 7t angularly overlap. The cams 46 and 47 have bores 78 and '79 respectively extending therethrough, coaxially with the cylinder axis to slidably receive the control member 42. The axial spacing between the cam surfaces 66 and 70 forms a continuous irregular cam slot or groove 80 angularly about the axis that has a ripsaw tooth pattern.

The indexing cams 46 and 47 could alternately be constructed integrally with each other with the cam surfaces 60 and 70 being formed by an irregular continuous slot or groove similar to slot 80 that extends angularly about the axis.

Control member 42 is illustrated in isolation in FIG. 7, having a cylindrical body 82 that is slidably mounted in the bores 78 and 79 for longitudinal movement along the longitudinal axis of the cylinder. At one end of the cylindrical body 82 is diametrically opposed cam followers or ears 83 and 34 that extend outward from the cylindrical body for moving in the groove and engaging the spirally-inclined surfaces 60 and 74). The cam followers 83 and 84 move along the continuously irregular cam slot 86 that is provided between the cam surfaces 60 and 70. The longitudinal movement of the control member 42 is limited to the distance between the dwells 62 and 74. As the control member is reciprocated longitudinally the cam followers 83 and 84 engage cam surfaces ill and 6th and follow the contour of the cam surfaces to incrementally index and rotate the control member 42 about the axis of the control member.

Interlocking means 44 includes an interlocking member 88 formed on the other end of the cylindrical body 82 and an interlocking element 90 formed in or affixed to the piston 3(1). In the specific embodiment illustrated, the interlocking element 88 is a male element having a reduced cylindrical cross-section at end 92. A crossbar 94 is formed integrally on the reduced end 92 with diametrically opposed ends 95, 96 projecting outward. The bar 94 has tapered sides 97 and 98. The interlocking element 9t] is a female element having a slot 100 formed in the piston in which the slot 100 has a width slightly greater than the width of the bar 94 to enable the bar to pass therethrough when the bar is angularly aligned with the slot MM). A cylindrical cavity 101 is formed in the piston communicating with the slot 100 forming abutment shoulders W2 and 103 on each side of the slots which face towardcylinder end IS. The cylindrical cavity llllll has a diameter slightly greater than the length of the bar 94 to enable the bar to rotate in the cavity WI with the bar 94 engaging the shoulders 102 and 103.

The bar 94 is angularly aligned with respect to the piston slot lltltl at two diametrically opposed angular positions of the control rod 42. The cams surfacesfll and 74) are angularly oriented about the cylinder axis so that the cam followers 533 and 84 are located in two diametrically opposed pockets 76 when the bar 94 is aligned with the slot lltMl).

The operation of the cylinder is illustrated in FIGS. 8413. In FIG. 8 the control member 42 is angularly oriented so that the cam followers 83 and 84 are located in said two diametrically opposed pockets 76 with the locking bar 94 aligned parallel with the slot M190.

As the piston moves toward the piston end 12 by the application of fluid pressure in chamber 33, the bar 94 enters the slot I00 (FIG. 9). The continued movement of the piston results in the engagement of the piston with the control member 42 with the bar 94 having passed through the slot lltMll into the cylindrical cavity lltll. The control member 42 is then moved longitudinally coincident with the piston removing the cam followers 83 and 84 from the pockets 76 and directing the cam followers against two of the inclined cam surfaces 64% The inclined cam surfaces 611 rotate the control member 42, in response to the longitudinal movement of the control member, from the alignment position approximately 45 until the cam followers 83 and 84 reach pockets 64 (FIG. lltl). As the control member 42 rotates, the bar 94 rotates in the cavity lltlll out of alignment with the slot 100 to effectively interlock the interlocking members 8% and 90, thus operatively securing the piston to the cylinder housing. As the fluid pressure from the expandible chamber 33 is released the piston starts back toward end carrying the control member 42. The control member 42 moves in a limited longitudinal stroke to remove the cam followers 83 and 34 from the pockets 64 and to direct to cam followers b3 and 44 against the offset spirally-inclined surfaces 70 as illustrated in FIG. 12. Continued movement of the piston results in the spirally-inclined cam surfaces 70 indexing the control member 42 an additional 45 to align the bar 94 substantially perpendicular to the slot lltlil with the ends 95 and 9b engaging the shoulders W2 and 103 to firmly hold the piston to the control member 42. When the cam followers b3 and 34 reach the pockets 76 the control member 42 has reached the end of its limited stroke thereby preventing the piston from further movement toward end 15. It should be noted that the piston will be automatically held in this position even though there should be a failure of the fluid pressure system.

When it is desired to unlock the piston 30 from the housing 23, fluid pressure is again applied to the expandible chamber 3% to direct the piston again toward the one end 12 to push thevcontrol member 42 in the limited axial movement to engage the cam followers b3 and d4 with the inclined spiral surfaces 60 to index the control member in the same rotational direction an additional 45 (FIG. 13). When the fluid pressure is again released from the expandible chamber 34 the control member 42 moves in a limited return stroke with the piston to direct the cam followers 83 from the pockets 64 and against the spirally-inclined surfaces 70 to index the control member 42 approximately an additional 45 to again align the bar 94 parallel with the slot MM) to enable the piston to move freely from the control member towards the piston end 115.

Thus, it can be seen that the piston is automatically locked and unlocked with the housing 23 every time fluid pressure is applied in expandible chamber 3% and then released.

in the preferred embodiment the control member is indexed approximately 90 during each cycle of operation in which the piston is driven to the piston end 12 and then permitted to move toward the piston end 115 in the limited stroke.

The number of inclined cam surfaces as and 70 may be varied and the configuration of the interlocking members 44 and 90 may be varied to provide the desired interlocking arrangement in response to the angular rotational movement of the control member to automatically unlock and lock the piston with the control member.

Furthermore, it should be appreciated that the principles of this invention are met by having the control member 42 rotatably mounted on the piston 27 with longitudinal slots being provided in the cam 47 to enable the cam followers 43 and $4 to move through the slots to and from the angular cam slot b ll.

It should be understood that the above described embodiment is simply illustrative of the principles of this invention and that numerous other embodiments may be readily devised by those skilled in the art without deviating from the principles thereof. Therefore, only the following claims are intended to define this invention.

What i claim is:

1. An automatic self-locking fluidized cylinder, comprising:

a cylinder housing having an enclosed elongated fluid receiving cavity therein between two ends;

a piston mounted in the cavity for longitudinal movement between the ends in response to the application of fluid pressure thereto;

a releasable locking means responsive to the movement of the piston at one end for (1) automatically operatively locking the piston to the housing at the one end when fluid pressure is applied to the piston to drive the piston to the one end and the pressure is then released and (2) for automatically releasing the operatively locked piston to permit the piston to return to the other end when fluid pressure is subsequently applied to the piston in the same direction and the pressure is then released, in which the releasably locking means includes;

a control member mounted with respect to the housing (1) for rotational movement about an axis parallel with the movement of the piston to and from a prescribed angular position, and (2) for axial movement in a path along the axis in response to the movement of the piston at said one end;

means for angularly rotating the control member to and from the prescribed angular position in response to the axial movement of the control member to position the control member angularly displaced the prescribed angular position when fluid pressure is applied to the piston to drive the piston to the one end and the pressure is then released and to position the control member at the prescribed angular position when fluid pressure is subsequently applied to the piston in the same direction and the pressure is then released; and

interlocking means responsive to the rotational movement of the control member for operatively interconnecting the piston to the housing when the control member is rotated from the prescribed angular position and for releasing the piston from operatively interlocking with the housing when the control member is rotated to the prescribed angular position.

2. The self-locking cylinder as defined in claim ll wherein the means for angularly rotating the control member includes:

cam means mounted in the path of the control member for engaging and angularly rotating the control member to and from the prescribed angular position in response to the axial movement of the control member. 3

3. The self-locking cylinder as defined in claim 2 wherein the cam means includes at least two oppositely inclined axially spaced step indexing cam surfaces angularly overlapping and extending about said axis; and

wherein the control member has a cam follower for engaging and following the inclination of said cam surfaces as the control member is moved axially in response to the movement of the piston to rotatably index the control member to and from the prescribed angular position.

4. The self-locking cylinder as defined in claim 3 wherein the piston has an interlocking element carried thereby and wherein the control member includes a body that is slidably mounted with respect to the housing adjacent the one end, said body having an interlocking element carried thereby which interlockingly engages with the piston interlocking element when the control member is angularly displaced from the prescribed angular position and interlockingly disengages with the piston interlocking element when the control member is angularly positioned at the prescribed angular position.

5. A self-locking cylinder as defined in claim 3 wherein the cam means includes two axially spaced opposed cams, one cam being positioned to engage the cam follower when the control member is being moved in one axial direction as the piston approaches said one end and the other cam being positioned to engage the cam follower when the controlmember is being moved in the other axial direction as the piston starts back from the one end towards the other end, each of said cams having a plurality of equally spaced cam surfaces that are directed in the same rotational direction, with each cam surface overlapping a corresponding surface of the opposed cam to step index the control member about its axis and as the control member is moved axially.

6. The self-locking cylinder as defined in claim 5 wherein the control member is rotatable to and from two diametrically opposed prescribed angular positions and wherein each of the cam surfaces extend in the same radial direction from a lobe to a dwell in which the dwells of each cam are angularly spaced approximately 90 from each other with the dwells of one cam being angularly offset from the dwells of the other cam to cause the control member to rotate 90 each time the control member is moved in one axial direction and then moved in the other axial direction.

7. The self-locking cylinder as defined in claim 6 wherein the locking means includes an interlocking element carried by the piston and a complementary interlocking element carried by the control member to releasably interlock with each other to secure the piston to the control member when the piston is adjacent said one end, said interlocking elements being releasable when the control member is rotated to the diametrically opposed prescribed angular positions.

8. The self-locking cylinder as defined in claim 1 wherein the locking means includes an interlocking element carried by the piston and a complementary interlocking element carried by the control member in which the interlocking elements are adapted to interlock with each other and secure the piston to the control member when the control member is rotated from the prescribed angular position.

9. The self-locking cylinder as defined in claim 8 wherein one of the interlocking elements has an interior angular shoulder facing said other end of the cavity with a longitudinal slot formed in the shoulder at an angular position corresponding to the prescribed angular position of the control member and wherein the other interlocking element has a radial projection adapted to be inserted into the slot when the piston is moved to said one cavity end and for being rotated in response to the movement of the control member from the prescribed angular position to engage said shoulder when the piston starts toward the other cavity end to prevent the piston from returning to the other cavity end.

10. The self-locking cylinder as defined in claim 5 wherein the cams are continuous about the axis with the cam surfaces of each cam interconnected to limit the axial movement of control member to a limited 

1. An automatic self-locking fluidized cylinder, comprising: a cylinder housing having an enclosed elongated fluid receiving cavity therein between two ends; a piston mounted in the cavity for longitudinal movement between the ends in response to the application of fluid pressure thereto; a releasable locking means responsive to the movement of the piston at one end for (1) automatically operatively locking the piston to the housing at the one end when fluid pressure is applied to the piston to drive the piston to the one end and the pressure is then released and (2) for automatically releasing the operatively locked piston to permit the piston to return to the other end when fluid pressure is subsequently applied to the piston in the same direction and the pressure is then released, in which the releasably locking means includes; a control member mounted with respect to the housing (1) for rotational movement about an axis parallel with the movement of the piston to and from a prescribed angular position, and (2) for axial movement in a path along the axis in response to the movement of the piston at said one end; means for angularly rotating the control member to and from the prescribed angular position in response to the axial movement of the control member to position the control member angularly displaced the prescribed angular position when fluid pressure is applied to the piston to drive the piston to the one end and the pressure is then released and to position the control member at the prescribed angular position when fluid pressure is subsequently apPlied to the piston in the same direction and the pressure is then released; and interlocking means responsive to the rotational movement of the control member for operatively interconnecting the piston to the housing when the control member is rotated from the prescribed angular position and for releasing the piston from operatively interlocking with the housing when the control member is rotated to the prescribed angular position.
 2. The self-locking cylinder as defined in claim 1 wherein the means for angularly rotating the control member includes: cam means mounted in the path of the control member for engaging and angularly rotating the control member to and from the prescribed angular position in response to the axial movement of the control member.
 3. The self-locking cylinder as defined in claim 2 wherein the cam means includes at least two oppositely inclined axially spaced step indexing cam surfaces angularly overlapping and extending about said axis; and wherein the control member has a cam follower for engaging and following the inclination of said cam surfaces as the control member is moved axially in response to the movement of the piston to rotatably index the control member to and from the prescribed angular position.
 4. The self-locking cylinder as defined in claim 3 wherein the piston has an interlocking element carried thereby and wherein the control member includes a body that is slidably mounted with respect to the housing adjacent the one end, said body having an interlocking element carried thereby which interlockingly engages with the piston interlocking element when the control member is angularly displaced from the prescribed angular position and interlockingly disengages with the piston interlocking element when the control member is angularly positioned at the prescribed angular position.
 5. A self-locking cylinder as defined in claim 3 wherein the cam means includes two axially spaced opposed cams, one cam being positioned to engage the cam follower when the control member is being moved in one axial direction as the piston approaches said one end and the other cam being positioned to engage the cam follower when the control member is being moved in the other axial direction as the piston starts back from the one end towards the other end, each of said cams having a plurality of equally spaced cam surfaces that are directed in the same rotational direction, with each cam surface overlapping a corresponding surface of the opposed cam to step index the control member about its axis and as the control member is moved axially.
 6. The self-locking cylinder as defined in claim 5 wherein the control member is rotatable to and from two diametrically opposed prescribed angular positions and wherein each of the cam surfaces extend in the same radial direction from a lobe to a dwell in which the dwells of each cam are angularly spaced approximately 90* from each other with the dwells of one cam being angularly offset from the dwells of the other cam to cause the control member to rotate 90* each time the control member is moved in one axial direction and then moved in the other axial direction.
 7. The self-locking cylinder as defined in claim 6 wherein the locking means includes an interlocking element carried by the piston and a complementary interlocking element carried by the control member to releasably interlock with each other to secure the piston to the control member when the piston is adjacent said one end, said interlocking elements being releasable when the control member is rotated to the diametrically opposed prescribed angular positions.
 8. The self-locking cylinder as defined in claim 1 wherein the locking means includes an interlocking element carried by the piston and a complementary interlocking element carried by the control member in which the interlocking elements are adapted to interlock with each other and secure the piston to the control member when the control member is rotated from the prescribed angular position.
 9. The self-locking cylinder as defined in claim 8 wherein one of the interlocking elements has an interior angular shoulder facing said other end of the cavity with a longitudinal slot formed in the shoulder at an angular position corresponding to the prescribed angular position of the control member and wherein the other interlocking element has a radial projection adapted to be inserted into the slot when the piston is moved to said one cavity end and for being rotated in response to the movement of the control member from the prescribed angular position to engage said shoulder when the piston starts toward the other cavity end to prevent the piston from returning to the other cavity end.
 10. The self-locking cylinder as defined in claim 5 wherein the cams are continuous about the axis with the cam surfaces of each cam interconnected to limit the axial movement of control member to a limited stroke. 